Telephone system



March 31," 1936: H. c. CURL 2,036,023

TELEPHONE SYSTEM Filed June 9, 1933 1 8 Sheets-Sheet l7 FIG.

FIG. 2 FIG. 3 FIG. 4

FIG. 5 FIG. 6 FIG. 7

MASTER SWITCH INVENTOR H. C. CURL ATTORNEY March 31, 1936. CURL 2,036,023

TELEPHONE SYSTEM Filed June 9, 1935 8 Sheets-Sheet 2 INVENTOR H, C CURL A 7' TORNE V March 31, 1936. Q CURL 2,036,023

TELEPHONE SYSTEM Filed June 9, 1933 88heets-Sheet 3 FIG. 3

INVENTOR H. C. CURL March 31, 1936. H. c. CURL 2,036,023

TELEPHONE SYSTEM Filed June 9, 1933 8 Sheets-Sheet 4 I---- INVENTOR H. C. CURL Br AZmIgA/EV March 31, 1936. q CURL 2,036,023

, TELEPHONE SYSTEM Filed June 9, 1935 8 Sheets-Sheet 5 FIG. 5

INVENTOR C. CURL ATTORNEY TELEPHONE SYSTEM Filed June 9; 1933 8 Sheets-Sheet 6 FIG. 6

INVNTOR H. a CURL ATTORNEY March 31, 1936. H. Q CURL 2,036,023

TELEPHONE SYSTEM Filed June 9, 1953 8. Sheets-Sheet 7 INVE'N7UR h. C. CURL ATTORNEY Patented Mar. 31, 1936 TELEPHONE SYSTEM Herbert G. Curl, Bayside, N. Y., assignor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application June 9, 1933, Serial No. 675,051 5 Claims. (01. 179-1) This invention relates to announcing telephone systems and the object of the invention is to pro- .vide such a system comprising two or more unit systems which may be operated entirely independently or as one complete system, as desired. Heretofore there have been proposed systems comprising a number of transmitting stations, 2. common amplifier and a' number of groups of loudspeaking receivers selectively controllable from any one of the several stations. Some of these systems have been arranged'so that when one station is using the system all the others are locked out, but in an emergency any other station: may cut in andobtain joint (or sole) control of any desired receiver groups;

According to the present inventiontwo or more of these systems are so interconnected that any transmitting station may control the' receivers 01' the othersystems as well as its own receivers in exactly the same manner as if the several systems were originally designed as a single system having one amplifier and a number of transmitting stations equal to the total number in the several systems. More specifically this is accom-. plished by parallelling the several amplifiers and providing in each unit system suflicient circuits for the operation of the total number of stations and loudspeakers in thecombined system. These interconnections are preferably arranged to be made by a single masterswitch sothatajchange from unitto system operation or viceversa can be made without delay. v

A further feature of the invention is signaling means adjacent each receiver so that the operator may be requested to repeat the message or be advised that the message is understood. These circuits are also interconnected between systems to function oneither a unit or system basis.

These and other features of the invention will be more clearly'understood from the following detailed description and the accompanying drawtaken together, show a second complete unit system; and

Fig. 8 shows the master switch for combining the unit system.

The first unit system comprises essentially two transmitting stations I and 2, an amplifier 3 and six groups of receivers 4 to 9. The-second unit system similarly comprises station 20! and 202, an amplifier 203 and four groups of receivers 2M to 201. Only one receiver is indicated for each group but it will be understood that any desired number of loudspeaking receivers 01'' headsets or combinations thereof may be operated in one group. Similarly, while only two transmitting stations are shown in each system it will be obvious from the connections shown and described 10 below how any desiredadditional stations may be added to the system.

The amplifiers 3 and 203 have been shown with two conventional stages primarily for the purpose of showing the manner of interconnecting 15 them for combined system operation as described below. In actual practice a number of additional stagesmay be required. Ordinarily, a single common battery would be provided for the entire relay control system but individual batteries have been indicated wherever necessary, to simplify the wiring. Station I, which is typical of all four stations of the two systems, is equipped with a. transmitter l0, indicating lamps II and l2,-ten receiver group selective keys I3 to 22 and ten corresponding receiver group indicating lamps 23 to 32. The first six lamps 'and keys at all stations are associated with the six receiver groups of the first unit system'and the last four lamps and keys are associated with the four receiver groups of the second unit system. A non-locking key 33 is'provided for extinguishing the signal lamps whenan announcement has been completed and a locking key or cut-in switch 34 35 enables the stationto cut in its transmitter while another station is using the system.

Normal operating priority between the several stations is obtained by means of priority relays ority relay is operated in each unit system from each. station of the combined system.

The operation of the system will be explained by first describing the operation of a unit system and then by showing how the same operating feaceiver group selecting relays.

tures are obtained when the unitsare functioning as one complete system. 7

When the Operator of station I has a message to deliver he inserts plugs 35 and 38 of his transmitter in the jacks 31, 38 and operates one or more of the locking keys I3 to I8 according to the number of receiver groups to be connected. He then closes the hand operated contact 38 on his transmitter to complete a circuit extending from ground at the'jack 38 over conductor 48, the winding of his priority relay 4|, conductor 42, back contact 43 of priority relay 44 of station 2, conductor 45, back contact 48 of priority relay 41, conductor 48, back contact 48 of priority relay 58 to the grounded battery 5|.

The operation of relay 4| in closing contact 52 completes a circuit for the lamp II at station I and the lamp I I I at station 2 to indicate that the system is in use. Contact 53 of the relay completes the operating circuits of the relays 54 and 56 from grounded battery 85 over the conductor 51. The breaking of contacts 58, 58 and 88 of relay 4| opens the return circuit leading over conductors 8|, 82 and 63 to the windings of the other priority relays 44, 41 and 58 respectively. Con-' tact 58, therefore, disables relay 44 so that station 2 can not operate it in the usual manner by means of the transmitter switch 84.

The operation of relay 54 completes a circuit from the transmitter I8 over conductors 88 and 81, through the contacts on the relay to the conductors 88, 68 leading to the input circuit of the amplifier 3. The operation of relay 58 operates the receiver group selecting relays 18 to 15 by completing at contacts 18 to 8| the circuits previously prepared by the closing of the keys -I3 to I8 at the transmitting station. In order to obtain the same volume level irrespective of the number or receiver groups connected to the amplifier, these relays 18 to 15 are equipped with substitute load resistors suchas 82 which, when connected, introduce a loss in the system equal to the power consumed by the loudspeaking receiver group associated with the relay. The operation of these relays disconnects these substitute load resistors and connects the output leads 83, 84 of the amplifier directly to the receivers. The transmitter I8 is then connected to the receivers and the operator proceeds to deliver his message over the conductors 88, 81 and 88, 88 to the input of the amplifier 8 and from the output of the amplifier over the conductors 83, 84 to the receivers.

If station'2 desires to use the system when it is not already in use a similar series of operations take place, that is to say the transmitter of station 2 is connected to vits jack and the receiver group selecting keys corresponding to the desired receiver groups are operated to prepare the operating circuit of' the receiver group selecting relays 18 to 15. The closing of contact 84 on the transmitter operates priority relay 44 which lights the lamps II and II I, as before, opens the operating circuits of the other three priority relays and closes contact 88 to complete the operating circuits of relays 88 and 81. The operation of relay 88 connects the transmitter talking circuit to the conductors 88 and 88 leading to the input of the amplifier 8 and the operation of relay 81 completes the operating circuit of the selected re- If, however, the system is already in use by station .I when the operator at station 2 desires to make an announcement, he is advised of that fact by his lamp III but if he ignores this lamp and closes his contact 84, he can not operate his priority relay 44 since,

as already pointed out, the previous operation of relay 4| has opened the operating circuit of this relay at contact 58. If the circumstances warrant emergency action he may, however, close his cut-in switch 88, which completes a circuit extending from ground through the switch and conductor 88 to the cut-in relay 88 and back to ground through the battery 8 I. The operation of the relay 8,8 prepares an operating circuit for the priority relay 44 independently of contact 58 on priority relay 4| .so that upon closing the transmitter switch 64 the operating circuit for relay 44 extends from ground at the transmitter to the switch 64, conductor 82, winding of relay 44, to grounded battery 8|. The operation of relay 44 thereupon operates relays 88 and 81 as before and connects to the amplifier 3 any groups of receivers selected at station 2 but not already conneoted to the system by station I. The operator at station 2 may then proceed to deliver his emergency ,message. Upon the completion of his message he merely releases his transmitter switch 84 thereby releasing the priority relay 44 and the transmitter and receiver control relays 88 and 81. The locking key 88 is also released to release relay 88 and restore the system to normal operating condition.

Conveniently located with respect to the loudspeakers of each group is a locking key and a non-locking key. If a message delivered to receiver group 4, for example, is not understood, the non-locking key 83 is closed on contact 84 to operate the signal lamp relay 85 over a circuit extending from ground, conductor 88, winding of the relay, conductor 81, back contact 88 of relay 88 to grounded battery. The operation of relay 85 lights lamp 23 at the transmitting station over an obvious circuit. The key 88 is then released to extinguish the lamp and then reclosed to relight it repeatedly as a signal that the message has not been understood. The operator will then repeat the message and when it has been understood the key IN is closed to operate relay'85 over a circuit extending from ground, the back, normally closed contact of the key 83, conductor I82, key "I, conductor 88, winding of the relay to grounded battery. The operation of the relay closes contact I83 to maintain the operating circuit of the relay independently of the key I8 I. This maintains the lamp 28 lighted as an' indication that the message has been understood. When the message has been understood by all the receiving operators and the station operator is disconnecting his station from the system as previously described for station 2, he also momentarily closes his key 88 at the station to operate relay 88 and open contact 88 which releases relay 85 and any other signal lamp relays which have been locked up.

The operation of stations MI and 282 is identical with the operation of stations I and 2 already described so that for unit operation of the system no detailed discussion of the circuit of the second unit system need be given.

When it is desired-to operate the two units as one combined system, the master switch 288 is moved to the left to make the necessary additional interconnections between the systems.

Many of the interconnections which do not intering lamps at station 2, both of which relate to the receiver group in the second unit system, extends to ground through contact 2I8 of the switch 200 so that for unit operation contact 2I8 is opened and these lamps will not be lighted when the answer-back signals are being sent to stations 20I and 202. Similarly, the return circuit of the first six lamps at stations 20I and 202 extend to ground through contacts 263 to prevent signals intended for stations I and 2 from appearing also at stations 20I.and 202. It will be noted that for unit operation the output circuit of the vacuum tube I04 of the amplifier 3 is shunted by a resistor I05 overa circuit including conductor I06, contact I01 of the switch 200, the resistor I05 and conductor I06. Similarly, the output circuit of the vacuum tube I09 of the amplifier 203 is shunted bya resistor I I8 over a circuit including conductor I I6, the resistor, contact I I 3 of the switch 200, and conductor II4. When the master switch 200 is moved to the left contacts I01 and I I3 are broken and the amplifiers 3 and 203 are paralleled between their stages over the following circuit. From the plate of tube I04 over'conductor I06,

contact I I5 of the master switch, conductor I I6 to the plate of the tube I09 in the amplifier 203. The plate circuit returns are also paralleled over a circuit extending from conductor I08 in theamplifier 3, contact II1 of the master switch to conductor I I4 leading to the amplifier 203. 'Under this condition, any messages transmitted to either of the vacuum tubes I04 or I09 will be transmitted to the output circuit of both the amplifiers 3 and 203 to energize any of the selected groups of receivers in both systems. The resistors I05 and H8 are of such value that when the amplifiers are parallelled and the resistors disconnected, transmission is not affected.

If the operator at station I now operates his priority relay 4I to lock out station 2 in the manner already described, the priority relay MI in the other unit system will also be operated over a circuit extending from conductor 40, conductor 208, contact 209 of the master switch, conductor 2 I0, Winding of the relay 24I, conductor 2I I, contact 2I2 of the relay 244, conductor 2I3, contact 2I4 of the relay 241, conductor 2I5, contact 2I6 of the relay.250 to grounded battery 2I1. The

. operation of relay 24I opens the operating circuit of the relays 244, 241 and 250 so that stations 20I and 202 are also locked out. Station I may thenproceed to select any or all of the first six loudspeaker groups associated with'his system and,

in addition, one or more of the four groups assoj ciated wtih the other unit system. For example,

he may close all ten keys I3 to 22.

The receiver groups 4 to 9 will be selected in the manner already described and in addition the closing of keys I9 to 22 will select the receiver groups 204 to 201 in the following manner: A circuit is made from ground at the master switch through contact 2I8, conductor 266, keys I9 to 22 over all four conductors 2I9 to 222, through the upper four contacts of the relay 56 which has already been operated to conductors 223 to 2 26 and conductors 221 to 230 to grounded batteries through the relays 23I to 234. The operation of these relays disconnects the substitute load resistors and connects the loudspeaker groups 204 to 201, through the conductors 235 and 236 to the output circuit of the amplifier 203. By virtue of the parallel connection between the amplifiers these receiver groups will then be energized by messages sent from station I simultaneously with the receiver group in the first unit system. Since the signal lights 29 to 32 in the station I and the corresponding lamps are now connected to ground on one side by conductor 2I9 and connected in parallel with the corresponding lamps in stations 20I and 202 by conductors 230, 230, 240 and 242, they may be operated for signal purposes from the receiver groups 204 to 201 in the same manner as the corresponding lamps in stations 20I and 202 when these receiver groups are energizedfrom one of the stations in that unit system.

In an emergency the operator at station 2 may, by means of the switch 08, cut in his transmitter in exactly the same manner as for unit operation and either station 20I or 202 may also cut in in a similar manner. For example, the operation of the switch 25I completes a circuit forcut-in v 59 of relay 4|, extending from battery I54, winding and relay 41, conductor I55, contact I56 of the master switch, conductor 243 to ground through the transmitter switch 239. The operation of relay 41 lights lamp I2 and H2 in stations I and 2, respectively, over a circuit extending from grounded battery I51, conductors I58 and I59. through the lamp to conductor 2I9 and ground at the master switch. These lamps give an indication at stations I and 2 that one of the stations 20I or 202 is using the system. The operation of lelay 252 operates relay 241 independently of the relay 24I which has already been operated by station I, over a circuit from battery 254, through the relay 241 to ground through the transmitter switch 239. In closing contact 251, relay 241 operates relay 258 to connectthe transmitter 259 to the amplifier 203 and relay 260 to prepare operating circuits for the selecting relays of any desired receiver groups not already connected by station I. Station 201 may then proceed to deliver a message to all the selected receiver groups and when finished disconnect his station from the system as already described for station I. When it is desired again to use the system as two independent units it is only necessary to restore the master switch to the position shown and the combined system is immediately reconverted to 7 two independent systems with their original operating features It will be seen from the foregoing description that for unit operation lamps II. and-III are lighted when either station I or 2 is operating and lamps 245 and 248 are lighted when either station 20I or 202 is operating. For the combined system operation, lamps II, III, 246 and 249 are lighted when either station I or 2- is operatin and lamps I2, H2, 245 and 248 are lighted when either station 20I or 202 is operating. When one or more stations of each unit system is operating, both lamps at all four stations will be lighted. If, for example, the operator illustration, it will be understood that various changes may be made within the scope of the following claims.

What is claimed is:

1. In an announcing system the combination with at least two normally independent unit systems each including a plurality of transmitting stations, an amplifier, a plurality of receivers, means at each of the stations for connecting the stations and the receivers to the amplifier, means operated when one of the stations is so connected for disabling the other station, and emergency means at each station operable while,the station is disabled for connecting it to the amplifier, of cross connections between the unit systems and a switch therein for effectively combining the unit systems into a single system in which each transmitting station may control all the receivers in the same manner as it controls the receivers in the corresponding system when operating as an independent unit.

2. In an announcing system the-combination with at least two normally independent unit systems each including a plurality of transmitting stations, a priority relay in each system for each station in all the unit systems, an operating circuit therefor, an amplifier, a' plurality of receivers, a receiver-control relay for each receiver in all the unit systems, an operating circuit therefor, means at each station for operating the corresponding priority and receiver-control relays of said unit systems to connect the stations and the receivers to the amplifier, and contacts on said priority relays for opening the operating circuits of the other priority relays, of cross connections between the unit systems and a switch therein for paralleling the amplifiers and the operating circuits of the corresponding priority and receiver-control relays of the several systems.

3. In an announcing system the combination with a plurality of transmitting stations, an amplifier, a plurality of receivers, and means at the stations for selectively connecting the receivers and the stations to the amplifier, of a plurality of indicators at the stations, means at each receiver for operating an indicator at each station, and means at each station for resetting operated indicators.

4. In an announcing system, the combination with at least two normally independent unit systems each including a plurality of transmitting stations, an amplifier, a plurality of receit .;1'S, means at each of the stations for connecting the stations and the receivers to the amplifier, and

an impedance normally connected in shunt to the amplifier, of cross connections between the unit systems, a switch therein for efiectively combining the unit systems into a single system, and contacts on the switch for paralleling the amplifiers and disconnecting said impedance.

5. An announcing telephone system comprising at least two normally independent unit systems each including a plurality of transmitting stations and a plurality of receiver circuits selectively controllable therefrom, a priority relay in each unit system for each station of all the unit systems, an operating circuit for each relay extending through the contacts of each of the other relays of the unit system, and controllable from the corresponding station, means responsive to each priority relay for completing a talking circuit between a transmitting station and selected receiver circuit, and means for combining the unit systems into a single system comprising a switch and contacts thereon paralleling the talking circuit and the corresponding priority relay of the unit systems.

HERBERT C. CURL. 

